Some empirical studies show negative consequences of being demographically different from one's group, but the underlying psychological mechanisms are not well understood. To address this gap, we investigated the role of the belonging and distinctiveness motives in individuals' experiences of being ethnically dissimilar from their group. We propose that ethnic dissimilarity satisfies group members' need for distinctiveness whereas it frustrates members' need for belonging, and this frustration reduces their organizational attachment. An experimental study showed that ethnic dissimilarity led to heightened arousal of the belonging motive, indicating that this motive was frustrated. In a naturalistic study of real-life student groups, ethnic dissimilarity was associated with frustrated belonging, which in turn was associated with reduced organizational attachment. This paper contributes to the literature of demographic dissimilarity in groups by closely examining the effect of demographic dissimilarity on group members' fundamental motives and reactions to group membership.Keywords: demographic dissimilarity; group diversity; belonging motive; distinctiveness motive; identity shift Running head: ETHNIC DISSIMILARITY AND THE BELONGING MOTIVE 2 Both academics and management practitioners highlight the value of demographic diversity, particularly with regards to group tasks. Diversity in work groups can lead to high quality group outcomes because of the varied perspectives and knowledge within the group (Cox, Lobel, & McLeod, 1991;McLeod, Lobel, & Cox, 1996), tolerance of dissenting ideas (Phillips & Loyd, 2006), and thorough information processing (Sommers, Warp, & Mahoney, 2008). However, diversity can also have detrimental effects on individual group members. Indeed, individuals who are demographically dissimilar from their group, at times, suffer from a host of individual problems, such as reduced satisfaction and commitment, as well as higher absenteeism and turnover (e.g., Chatman & Flynn, 2001;Guillaume, Brodbeck, & Riketta, 2012;Jackson et al., 1991;Liao, Joshi, & Chuang, 2004;Riordan & Shore, 1997;Tsui, Egan, & O'Reilly, 1992; but see Guillaume, Van Knippenberg, & Brodbeck, 2014).One key mechanism proposed to explain these negative effects is motivated identity construction, or how individuals define themselves to satisfy basic identity motives (Ashforth & Mael, 1989;Vignoles, 2011). Drawing on social identity (SIT; Tajfel & Turner, 1986) and self-categorization theories (SCT; Turner, Hogg, Oakes, Reicher, & Wetherell, 1987), group diversity researchers have suggested that group members routinely categorize themselves in relation to other members based on salient demographic Running head: ETHNIC DISSIMILARITY AND THE BELONGING MOTIVE 3 characteristics, and these self-definition processes affect members' experiences in groups through motive satisfaction/frustration (Chatman, Polzer, Barsade, & Neale, 1998;Tsui et al., 1992).Among several motives that can guide identity processes (Ashforth & Mael, 1989...